A favorite Las Vegas landmark is missing, and the Neon Museum is on the hunt for answers via Facebook.

The Neon Museum and Boneyard posted a photo of the Glass Pool Inn sign on its social media page Thursday, accompanied by the words “Have you seen this sign?”

The curvy blue sign that stood on Las Vegas Boulevard near Russell Road was being donated to the museum, but Danielle Kelly, the museum’s executive director, said she received a call Thursday from the facilitator of the donation, telling her that the sign has been missing since at least the end of May.

The sign was all that was left of the two-story motel with an above-ground pool with large, circular windows that allowed passers-by to see swimmers underwater. The motel, originally named the Mirage, was built in 1952 and demolished in 2006. It was widely photographed and featured in movies, including "Casino."

The sign was sitting on the property behind a locked fence. Nearby, construction is underway for SkyVue’s 550-foot tall observation wheel.

Kelly learned recently that the Glass Pool Inn sign had been taken down when a workman working on Las Vegas Boulevard called to tell her he had seen people digging through the scraps of the Casa Malaga sign, which had fallen apart while being dismantled.

Given the size of the Glass Pool Inn sign and what its extraction would require, the sign might not have survived its removal from the lot. Kelly says she doesn’t know the exact dimensions, but that removing it from the property would require breaking the lock, driving in a large truck — possibly a crane — and the manpower of at least two people.

Unlike many of the older cabinet signs in the Boneyard, the Glass Pool Inn sign was made of a curvy metal perimeter and plexi, which can be damaged easily. If a crane wasn't used, Kelly says, it would have needed to be cut apart. The sign was made up of several parts, including another curvy piece that featured the word “slots” and the marquee box listing the hotel’s amenities.

The photo of the sign and the announcement that “someone stole it from the site” was posted on the Neon Museum and Boneyard’s Facebook page just before 4 p.m. Thursday.

“I’m concerned somebody stole it for scrap and that it’s probably gone,” Kelly says. “It’s sad. It has such a sentimental value for people. People loved that place.”